JP2003276075A - Apparatus and method for molding hollow molding - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an apparatus for molding a hollow molding which can prevent waving and sagging of a resin sheet by softening of the sheet, improve productivity, and reduce production costs. <P>SOLUTION: The apparatus has a fixing mechanism 15 for fixing the peripheral parts 4' of thermoplastic resin sheets 4 of a pair to form a closed space 13 between the sheets 4, a heating means 15 for heating and softening the sheets, and a mold which has a mold cavity surface for molding the sheets and clamps the insides of the peripheral parts of the softened sheets to press the sheets. The fixing mechanism has a pair of sheet holders 8 and 9 which hold the sheets at a prescribed distance and are mutually slidable, a driving means for shortening the distance between the sheets by driving at least one of the sheet holders, and a seal structure for sealing slide surfaces 12 of the sheet holders. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a molding device and a molding method for a hollow molded body.

[0002]

2. Description of the Related Art When a resin material is applied to an automobile part, it is required to be lightweight and have high rigidity and high strength. Therefore, a part having a hollow portion inside the resin (hollow molded body) has been developed. ing.

For example, Japanese Patent Laid-Open No. 8-323842 discloses that a honeycomb structure (insert) is preliminarily placed between two resin sheets made of a thermoplastic resin, the resin sheet is heated, and then a metal mold is used. It discloses a method of forming a hollow molded body by sandwiching the hollow molded body with.

In Japanese Patent Laid-Open No. 9-262899, a breathable heat-resistant support material (insert) is inserted between two resin sheets made of a thermoplastic resin to suppress sagging of the resin sheet due to softening. Disclosed is a method for molding a hollow molded body, which can prevent the contact and fusion of the resin sheet in the hollow portion.

[0005]

However, the method disclosed in the above publication has a problem that the molding cost and the number of steps are increased because it is necessary to prepare the insert in advance by molding or processing. Furthermore, when the resin sheet is transparent, the insert can be seen through, so that a completely transparent hollow molded article could not be obtained.

On the other hand, in the method of molding a hollow molded body which does not use an insert, the heat-softened resin sheet sags under its own weight. Therefore, when a large hollow molded body is molded with a vast resin sheet, there is a problem that, for example, the resin sheet is wavy in the hollow portion, or is contacted and fused.

The present invention has been made in order to solve the problems associated with the prior art described above, and can prevent the resin sheet from waviness and sagging due to heat softening, and
An object of the present invention is to provide a molding apparatus and a molding method for a hollow molded body, which can improve productivity and reduce manufacturing cost.

[0008]

According to a first aspect of the invention for achieving the above object, a peripheral edge portion of a resin sheet is formed so that a sealed space is formed between a pair of resin sheets made of a thermoplastic resin. A fixing mechanism for fixing, a heating means for heating and softening the resin sheet, and a mold cavity surface for shaping the resin sheet, and sandwiching the inside of the peripheral edge of the heat-softened resin sheet, A molding apparatus for a hollow molded body having a die for press-bonding, wherein the fixing mechanism holds a resin sheet at a predetermined interval and is slidable with respect to each other, and the sheet. A hollow molded article characterized by having a driving means for sliding at least one of the holders to reduce the distance between the resin sheets and a seal structure for sealing the sliding surface of the sheet holder. It is in the form equipment.

[0009]

The present invention described in the claims has the following effects.

According to the first aspect of the invention, after the resin sheet is softened by heating, at least one of the sheet holders can be slid in a sealed state to reduce the distance between the resin sheets.

As a result, the volume of the closed space formed between the resin sheets decreases and the internal pressure rises.
Even if the resin sheet is large, the resin sheet is prevented from waviness and sagging due to heat softening. Further, since the insert is unnecessary, the molding cost and man-hours do not increase, so that the productivity can be improved and the manufacturing cost can be reduced.

According to the second aspect of the invention, since the guide means is provided, the sliding position accuracy of the seat holder can be improved.

According to the third aspect of the present invention, since the driving force is applied to the driving means by the movement of the die, the structure of the driving means can be simplified.

According to the fourth aspect of the invention, the seal structure can be easily constructed.

According to the fifth aspect of the present invention, after the resin sheet is softened by heating, at least one of the sheet holders is slid in a sealed state to reduce the distance between the resin sheets.

As a result, the volume of the closed space formed between the resin sheets decreases and the internal pressure rises.
Even if the resin sheet is large, the resin sheet is prevented from waviness and sagging due to heat softening. Further, since the insert is unnecessary, the molding cost and man-hours do not increase, so that the productivity can be improved and the manufacturing cost can be reduced.

According to the invention described in claim 6, since the driving means is arranged only on one side of the mold, the structure of the driving means is simplified.

According to the invention described in claim 7, in order to shape the resin sheet which is softened by heating by the mold cavity surface, the vacuum forming method, the pressure forming method, or the vacuum pressure forming method is applied. be able to.

According to the invention described in claim 8, there is obtained a hollow molded article containing any one of an organic filler, an inorganic filler and a fiber reinforcing material, or a mixture of two or more thereof. You can

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view showing an example of a hollow molded body 20 obtained by a molding apparatus according to an embodiment of the present invention.

The hollow molded body 20 is formed by pressure-bonding a pair of resin sheets 4, and a hollow portion 21, a pressure-bonded peripheral edge portion 22, and a pressurized gas for forming the hollow portion. And the holes 23 used for feeding.

The material of the resin sheet 4 is not particularly limited as long as it is a thermoplastic resin (thermoplastic resin) that is softened by heating, and examples thereof include polyolefin resins such as polyethylene and polypropylene, polystyrene, polycarbonate.
General thermoplastic resins such as carbon dioxide, acrylonitrile / styrene / butadiene block copolymer, polyamide fiber, and thermoplastic elastomers such as ethylene / propylene block copolymer and styrene / butadiene block copolymer, or these A polymer alloy or the like can be applied.

Further, in the thermoplastic resin, various fillers such as talc and glass fiber, and wavelengths of visible light (380
It is also possible to blend a composite material in which a fine-grained material of the order of several tens of nm, which is much smaller than (˜770 nm), is blended.

Examples of the fine particle material include clay, talc, silica and the like. In addition, pigments, lubricants, antistatic agents,
It is also possible to mix various additives such as antioxidants.

The thermoplastic resin according to the present invention includes all of them.

For example, it is possible to apply a thermoplastic resin containing any one of an organic filler, an inorganic filler and a fiber reinforcing material, or a mixture of two or more thereof. In this case, it is possible to obtain a hollow molded article containing any one of an organic filler, an inorganic filler, and a fiber reinforcing material, or a mixture of two or more thereof.

Next, the molding apparatus according to the embodiment of the present invention will be described.

As shown in FIG. 2, the molds 1 and 2 (upper mold 1 and lower mold 2) of the molding apparatus are made of, for example, aluminum, and the mold cavity surface 1A on which the resin sheet 4 is molded. , 2A and a suction port 3 formed in the mold cavity surfaces 1A, 2A. The resin sheet 4 is
For example, it is made of acrylic and is 330mm x 330mm x
The plate thickness is 5 mm.

The mold cavity surfaces 1A and 2A are, for example,
150 mm long × 150 mm wide × 100 mm deep,
It has a box-shaped structure with a draft in the depth direction of 5 degrees and a corner R5. The pressing surface of the upper mold 1 and the lower mold 2 is 200 mm
It is × 200 mm, and is configured so that the entire circumference from the peripheral edge of the pressing surface to 25 mm inside can be pressure-bonded.

The material of the upper mold 1 and the lower mold 2 is not limited to aluminum, and, for example, iron-based, non-ferrous metal other than aluminum, ceramic-based, thermosetting resin material and the like can be appropriately used.

The suction port 3 is used for vacuuming (reducing pressure). Since the shape of the suction port 3 is transferred to the surface of the hollow molded body 20, a proper number of suction ports 3 are formed at the corners of the upper mold 1 and the lower mold 2, and the diameter thereof is 1 mm.
The following are preferred.

Furthermore, the molding apparatus according to the embodiment of the present invention, as shown in FIG. 3, is a heating device 15 for heating and softening the resin sheet 4 (heating it to a softening temperature or higher).
And a fixing mechanism for fixing the resin sheet peripheral portion 4 ′ so that a closed space 13 is formed between the resin sheets 4, and a pipe 11 for supplying a pressurized gas for forming the hollow portion 21. And a pressure adjusting mechanism having.

The heat source of the heating device 15 is, for example, hot air, far infrared rays having a maximum energy wavelength of about 4 μm, short-wavelength or medium-wavelength heat rays having a maximum energy wavelength of about 1 μm to 3 μm, and preferably thermoplastic. It is a far infrared ray having an output wavelength corresponding to the absorption wavelength of the resin.

The fixing mechanism has a pair of sheet holders 8 and 9 (upper holder 8 and lower holder 9) which hold the resin sheet 4 at a predetermined interval and are slidable with respect to each other.

The material of the upper holder 8 and the lower holder 9 is not particularly limited as long as it can withstand the heating temperature of the resin sheet 4, the temperature at the time of pressure and pressure and the generated stress, and for example, iron-based materials. , A non-ferrous metal, a ceramic-based material, or a thermosetting resin material, preferably an iron-based or non-ferrous metal material that is inexpensive and easy to process.

The upper holder 8 and the lower holder 9 use guide pins to fix the resin sheet 4 via the upper pressing plate 5 and the lower pressing plate 6. The size of the inner side of the resin sheet peripheral portion 4 ′ fixed by the upper holder 8 and the lower holder 9 is, for example, 300 mm.
× 300 mm. In addition, a hole portion into which the guide pin is fitted is formed in the resin sheet peripheral portion 4 '.

The fixing of the resin sheet 4 is not limited to the method of using the guide pin, and for example, a method of using a bolt, a method of using a hydraulic press or a pneumatic press, a hinge of a resin sheet peripheral portion 4 is used. It is also possible to apply a method of narrowing the pressure with a plate that holds the '.

Further, the upper holder 8 and the lower holder 9
Are connected by a cylindrical slide shaft 7, and the lower holder 9 is guided by the slide shaft 7 to move in parallel on the sliding surface 12 of the upper holder 8.

The sliding surface 12 is provided with a seal structure for preventing air leakage between the resin sheets 4 by applying a rubber seal to the lower holder 9 side. However, the seal structure is not limited to this, and it is also possible to apply, for example, a mechanical seal, a mechanism incorporating a low sliding material, or a structure in which the gap of the sliding surface 12 is 0.5 mm or less. .

The guide structure using the slide shaft 7 is preferable because it has good positional accuracy and the design of the seal structure for the sliding surface 12 is easy. However, for example, a slide guide directly provided on the sliding surface 12 or a cam floor or roller floor using a bearing can be used.

Inside the fixed resin sheet peripheral portion 4 ', the lower die 2 is lifted (the die moves),
Since it is sandwiched by the upper mold 1 and the lower mold 2, a driving force for translating the lower holder 9 is generated.

As a result, the space between the resin sheets 4 fixed by the upper holder 8 and the lower holder 9 (holder space) is shortened, so that the volume of the closed space 13 formed between the resin sheets 4 is reduced, Internal pressure rises. Therefore, for example, even if the resin sheet 4 is large, the resin sheet 4 is prevented from waving and sagging due to heat softening, and since an insert is not required, the molding cost and the number of steps are not increased, and the productivity is improved. It is possible to improve and reduce the manufacturing cost.

Further, the driving means for sliding the lower holder 9 to reduce the holder interval does not need to generate a driving force, so that the structure thereof is simplified.

The pressure adjusting mechanism includes a pipe 11 through which the pressurized gas passes and a valve 10 for controlling the supply of the pressurized gas.
And a control device (not shown), for example, when supplying a pressurized gas to the hollow portion 21 of the resin sheet formed by pressure bonding (pressing) by the upper mold 1 and the lower mold 2,
It is used when the interior of the hollow portion 21 is opened to the atmosphere immediately before the pressing is completed and the hollow molded body 20 is taken out.

The pipe 11 is, for example, an S having an outer diameter of 6 mm.
It is made of US304 and is installed so as to be positioned horizontally with respect to the surfaces of the upper die 1 and the lower die 2 and to protrude from the wall surface of the die cavity surface during pressing. As the material of the pipe 11, iron-based, non-ferrous metal, ceramic-based, resin-based materials and the like can be used.

The controller is used, for example, to control the supply time, supply pressure, supply start timing, etc. of the pressurized gas.

The pressurized gas is not particularly limited, and for example, air, nitrogen gas, carbon dioxide gas and the like can be used, and nitrogen gas is preferable. The supply pressure of the pressurized gas depends on the molding conditions and the resin material, and a value of 1 MPa or more can be applied, but it is preferably less than 1 MPa.

Next, a method of molding a hollow body using the molding apparatus according to the embodiment of the present invention will be described. The molding method includes a mounting step, a heating and softening step, a mold and holder moving step, a pressure bonding step, a molding step, and a trimming step.

First, in the mounting step, as shown in FIG. 3, two resin sheets 4 are separated by a predetermined holder interval by an upper holder 8 and a lower holder 9 (upper pressing plate 5 and lower pressing plate 6). Then, the resin sheet peripheral portion 4 ′ is fixed so that the sealed space 13 is formed between the resin sheets 4. The predetermined holder spacing is, for example,
Even if the resin sheet 4 that has been softened by heating hangs down, the distance is such that it does not come into contact or fuse.

In the heating and softening step, the resin sheet 4 is heated and softened by the heating device 15.

In the mold and holder moving process, the lower mold 2 is raised due to pressing. Then, as shown in FIG. 4, by moving the lower mold 2, the upper mold 1 and the lower mold 2 are moved.
The inside of the peripheral edge portion 4'of the resin sheet sandwiched by the ascends.

On the other hand, the resin sheet 4 is held by the upper holder 8 and the lower holder 9 via the upper pressing plate 5 and the lower pressing plate 6. Therefore, the lower holder 9 is driven by the resin sheet 4,
Sliding surface 1 of upper holder 8 along slide shaft 7
2 is translated.

By reducing the holder spacing,
The volume of the closed space 13 decreases and the internal pressure rises. Therefore, for example, even if the resin sheet is large, waviness and sagging of the resin sheet due to heat softening are prevented without using an insert.

In the pressure-bonding step, the upper mold 1 and the lower mold 2, which have reached the predetermined pressing position, sandwich the inside of the fixed resin sheet peripheral portion 4 ', and pressure-bond them. As a result, the closed space 13 formed between the resin sheets 4 constitutes the hollow portion 21. The pressing time is, for example, 60 seconds.

In the molding step, immediately after pressure-bonding, as shown in FIG. 5, in order to promote adhesion and shaping of the resin sheet 4 to the mold cavity surface, the pipe 11 is formed.
And the suction port 3 formed on the mold cavity surface is operated.

More specifically, for example, a pressurized gas of 0.5 MPa is supplied through the pipe 11 to increase the internal pressure of the hollow portion 21, and at the same time, the suction port 3 is used to use the mold cavity surface. The outer peripheral space 14 between the resin sheet 4 and the resin sheet 4 is depressurized (negative pressure). That is, in this forming step, the vacuum pressure forming method, which is a combination of the vacuum forming method and the pressure forming method, is applied. The temperatures of the upper mold 1 and the lower mold 2 are, for example, 80 ° C to 90 ° C.

In the trimming step, as shown in FIG. 6, after cooling is completed, the upper die 1 and the lower die 2 are opened to remove the peripheral edge portion 4'of the resin sheet and burrs to thereby form a hollow molded article. 20 is obtained.

FIG. 7 is a chart for explaining the physical properties of the hollow molded body formed by the molding apparatus according to the embodiment of the present invention. Comparative Examples 1 to 3 are different from Examples 1 to 4 in that they were obtained under molding conditions in which the holder spacing was not reduced.

The physical property evaluation items are shapeability, pressure-bonding property, contact mark, and comprehensive evaluation.

The shapeability was evaluated by the deep drawability and the transferability at the corner R5. The pressure-bonding property was evaluated by breaking the pressure-bonded portion with a hammer and peeling at the contact interface of the resin sheet.
The contact mark was evaluated by the contact mark between resin sheets and the presence or absence of fusion. Further, when the evaluation is good, it is represented by the symbol ◯, and when it is poor, it is represented by the symbol x.

In the comprehensive evaluation, when the shapeability, the pressure-bonding property and the contact mark are all good, the symbol o is shown, and in other cases, the symbol x is shown.

In Examples 1 to 4, a holder interval of 30 mm to 200 mm and a heating temperature of 160 ° C. to 200 ° C. were applied when the resin sheet was attached, but good results were obtained for all evaluation items. That is, it was possible to obtain a lightweight hollow molded article having good rigidity, strength, and joint strength.

On the other hand, in Comparative Example 1, the holder interval of 30 mm and the heating temperature of 160 ° C. were applied, and the pressure-bonding property and contact mark were good, but the shapeability (transferability) was poor and good. No hollow molding was obtained.

In Comparative Example 2, the holder interval of 30 mm and the heating temperature of 180 ° C. were applied, and the shapeability and the pressure-bonding property were good, but the resin sheets contacted and fused with each other during heating and softening, so that it was good. No hollow molding was obtained. No good molded product was obtained.

In Comparative Example 3, the holder spacing of 100 mm and the heating temperature of 180 ° C. were applied, and the contact marks were good, but the entire surface was not crimped and the pressurized gas leaked (pressure loss). However, a hollow molded article having good shapeability could not be obtained. That is, the shapeability and the pressure bonding property were poor.

The present invention is not limited to the above-mentioned embodiments, but can be variously modified within the scope of the claims.

For example, the vacuum pressure forming method is applied in the forming step, but the present invention is not limited to this, and the vacuum forming method is applied to bring the resin sheet 4 into close contact with the mold cavity surfaces 1A and 2A only by reducing the pressure. It is also possible to let. Alternatively, it is also possible to apply the pressure molding method and bring the resin sheet 4 into close contact with the mold cavity surfaces 1A and 2A only by the pressurized gas.

Further, the driving means for moving the lower holder 9 is provided with a driving force by moving the mold in order to simplify the structure, but as shown in FIGS. 8 and 9, it is independent. It is also possible to arrange the driving means 16 and 17 on the outer peripheral portion of either one of the upper mold 1 and the lower mold 2.

In this case, the holder interval can be shortened without contacting the resin sheet 4. The drive means 16 and 17 may be hydraulic, pneumatic, spring, or electric motor, for example.

Further, the driving means are the upper mold 1 and the lower mold 2.
It is also possible to arrange both.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an example of a hollow molded body formed by a molding device according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of a mold of the molding apparatus according to the embodiment of the present invention.

FIG. 3 is a cross-sectional view of the molding apparatus according to the embodiment of the present invention, which is a view for explaining an attaching step and a heat softening step.

FIG. 4 is a cross-sectional view for explaining a mold and holder moving process.

FIG. 5 is a cross-sectional view for explaining a pressure-bonding step and a molding step.

FIG. 6 is a cross-sectional view for explaining a trimming process.

FIG. 7 is a chart for explaining the physical properties of the hollow molded body formed by the molding apparatus according to the embodiment of the present invention.

FIG. 8 is a cross-sectional view for explaining a modified example of the molding apparatus according to the embodiment of the present invention.

FIG. 9 is a sectional view for explaining another modification of the molding apparatus according to the embodiment of the present invention.

[Explanation of symbols]

1 ... upper mold, 2 ... Lower mold, 1A, 2A ... Mold cavity surface, 3 ... Suction port, 4 ... Resin sheet, 4 '... perimeter, 5 ... Upper presser plate, 6 ... Lower presser plate, 7 ... slide shaft, 8 ... Upper holder, 9 ... Lower holder, 10 ... Valve, 11 ... pipe, 12 ... sliding surface, 13 ... closed space, 14 ... Outer space, 15 ... Heating device, 16, 17 ... Driving means, 20 ... Hollow molded body, 21 ... Hollow part, 22 ... the peripheral portion, 23 ... hole.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Shinkichi Torii             Nissan, Takaracho, Kanagawa-ku, Yokohama-shi, Kanagawa Nissan             Inside the automobile corporation (72) Inventor Katsuhiko Suzuki             Nissan, Takaracho, Kanagawa-ku, Yokohama-shi, Kanagawa Nissan             Inside the automobile corporation F-term (reference) 4F208 AA21 AB11 AC03 AG07 AH17                       MA01 MA02 MA03 MB01 MH06                       MJ22 MJ30 MK15

Claims (8)

[Claims] 1. A fixing mechanism for fixing a peripheral portion of a resin sheet so that an enclosed space is formed between a pair of resin sheets made of a thermoplastic resin, and a heating means for heating and softening the resin sheet. Has a mold cavity surface for shaping the resin sheet,
The inside of the peripheral edge of the heat-softened resin sheet is sandwiched,
A molding apparatus for a hollow molded body having a die for pressurizing and pressing, wherein the fixing mechanism holds a pair of sheet holders that hold a resin sheet at a predetermined interval and are slidable with respect to each other, the sheet Molding of a hollow molded article, characterized by having a driving means for sliding at least one of the holders to reduce the distance between the resin sheets, and a seal structure for sealing the sliding surface of the sheet holder. apparatus. 2. The molding apparatus for a hollow molded body according to claim 1, wherein the driving means has a guide means for guiding the sheet holder. 3. The molding apparatus for a hollow molded body according to claim 1, wherein the driving means applies a driving force by the movement of the mold. 4. The seal structure comprises a mechanical seal,
The hollow molded body molding apparatus according to any one of claims 1 to 3, further comprising one of a rubber seal and an easily sliding material. 5. A method of molding a hollow molded body using the hollow molded body molding apparatus according to claim 1, wherein a pair of resin sheets made of a thermoplastic resin is formed into a pair of sheets. The holder holds the resin sheets at a predetermined interval, fixes the peripheral edge of the resin sheet so that a hermetic seal is formed between the resin sheets, heats and softens the resin sheet, and slides with at least one of the sheet holders sealed. Then, the interval between the resin sheets is shortened, the inside of the peripheral edge of the heat-softened resin sheet is sandwiched by a mold, and pressure bonding is performed to form the resin sheet on the mold cavity surface. A method for molding a hollow molded article. 6. The method for molding a hollow molded article according to claim 5, wherein the driving means is arranged in one of the molds. 7. The hollow molded body according to claim 5, wherein a vacuum molding method, a pressure molding method, or a vacuum pressure molding method is applied to the molding method of the hollow molded body. Molding method. 8. The thermoplastic resin contains one of an organic filler, an inorganic filler, and a fiber reinforcing material, or a mixture of two or more thereof. 7. The method for forming a hollow molded body according to any one of items 1 to 7.